Scattered and reflected incident radiation can expose a radiation sensitive layer in regions in which exposure is not desired. The use of antihalation layers to prevent this unwanted exposure is well known. Typically these auxiliary layers contain a dye, known as antihalation dye, which absorbs the incident radiation. An antihalation layer may be: (1) a backing layer, positioned on the side of the support opposite that bearing the radiation sensitive layer or layers; (2) an undercoat layer, located between the support and the radiation sensitive layer; (3) an interlayer, situated between two radiation sensitive layers; and/or (4) a filter layer, located above the photosensitive layer or layers.
Photographic elements are often used in conjunction with equipment whose output is recorded by exposing the element with infrared radiation emitted by, for example, semiconductor laser diodes. For example, in the medical diagnostics field, digital information from, for example, computer assisted tomography equipment, is often output for viewing onto photographic elements. These elements are generally exposed with diode lasers which emit radiation whose wavelength is from about 730 nm to around 900 nm, generally around 800 nm. Other diode lasers emit around 750 nm, 780 nm, 820 nm, or 870 nm.
Photographic elements used in conjunction with such output devices often require antihalation layers. These layers require antihalation dyes which absorb in the indicated spectral regions. In addition to absorbing the radiation used to expose the photosensitive layer, the antihalation dye should leave little or no undesirable stain after the element is processed. Stain can adversely affect the quality of the image, potentially making the image unusable or, in the case of medical recording film, producing an improper diagnosis.
Indolinium dyes which absorb infrared radiation are known. Sato, Japanese Patent Application Publication 63-33477, discloses infrared sensitive light recording media containing certain sulfoalkyl substituted indolenium dyes. The dyes absorb infrared radiation so that pits are formed in the light recording media. Laganis, U.S. Pat. No. 4,882,265, the disclosure of which is incorporated by reference, discloses photographic elements comprising an antihalation backing containing certain indolenium dyes. The dyes disclosed by Laganis, however, produce low levels of dye stain and may leave undesirable residues in process equipment.